Potentiometric titration of base salts

POTENTIOMETRIC TITRATION OF LIDOCAINE HYDROCHLORIDE

Titration is carried out in the laboratory using:

A tittered sodium hydroxide solution of concentration [c] = 0.0496 M made up according to the European pharmacopoeia standards
A test sample of lidocaine hydrochloride: 72.5 mg raw material
A theoretical expected volume of NaOH from the burette (assuming that the raw material is pure):

calculation of the expected theoretical drop volume of soda burette, part 1

(1)

N.A.: Letting n_{lidocaïne.HCL} be the number of moles of raw material used in the titration, the following can be written:

calculation of the expected theoretical drop volume of soda burette, part 2

calculation of the expected drop volume of soda burette, part 3

Integration of this value in equation (1) gives:

calculation of the theoretical volume of expected drop of soda burette, part 4 and result

Therefore, if the lidocaine hydrochloride raw material is pure, we obtain, with the concentrations of the reagents used in this titration, 5.06 mL NaOH from the burette at the equivalence point.